Pulp storage tower and method of emptying same



July 14, 1953 J. c. F. c. RICHTER 5,378

PULP STORAGE TOWER AND METHOD OF'EMPTYING SAME Filed March 5, 1948 j/orney Patented July 14, 1953 PULP STORAGE TOWER 'ANDMETHOD O EMPTYING,SAME J ohan Christoffer Fredrik CarlfRichter, Karlstad,

1 Sweden, assignor to Aktiebolaget Kamyr, Karlstad,Sweden, a company ofSweden Application March 5, 1948, Serial No. 13,214

v In Sweden March 20, 1947 In the cellulose and paper-making industry itis often necessary to store pulp. Thick pulp, that is to say, pulphaving a consistency of to per cent dry matter, is usually stored inso-calIed pulp bins, that is to say, open receptacles which have acomparatively small height but are quite large so that they require alarge floor space. Even withsuch shallow receptacles the withdrawal ofthe thick pulp, which cannot be transported by pumping, involves certaindifficulties. Usually, the removal of the pulp is effected by means ofso-called pulp diggers over the upper rim of the receptacle, orby meansof scrapers from thebottom of the receptacle, or by means of powerfulwater jets. All these prior art methods involve, however, the use ofcomparatively complicated, expensive and power consuming apparatuses.

In order to save floor spaceuseis often made of high and narrowreceptacles, so-called storage towers. When such towers are used,however, the difliculties connected with the withdrawal of the pulp bythe use of themethods above mentioned, are further increased. When highstorage towers are used, there is also the risk of the withdrawal of thepulp becoming irregular due to the column of pulp in the tower having atendency to stick at intervals to the walls of the tower.

It is an object of the present invention to eliminate the saiddifliculties and to provide a very simple and efficient method ofemptying high consistency pulp from a storage tower into which the pulpis charged from the top of the tower. The invention is also concernedwith a simple and efiicient improvement in pulp storage towers forcarrying out this method. The essential characterizing feature of theinvention resides in the emptying ofthe pulp being effected by theintroduction of a liquid under pressure into the bottom of the towerbelow the pulp therein, such liquid serving to progressively displacethe column of pulp upward to the top of the tower thereby to effectdischarge of the pulp therefrom.

When thick pulp is displaced upward in the tower in this manner by theintroduction of water into the bottom of the tower, it has been foundthat dilution of the pulp occurs only at the contact surface between thepulp and the water if the so-called flotation action is utilized. Suchflotation action is due to the fact that thick pulp contains larger orsmaller quantities of air which produces flotation, that is to say, thepulp will float on the water introduced into the tower 14 Claims.

2 I with an air cushion between the pulp and the water. If for anyreason the thick pulp charged into the tower does not contain thequantity of air required for floating the pulp on the water, the presentinvention provides for the introduct'ion of a suitable quantity or airsimultaneously with the displacement liquid into the bottom ofthe tower.

In the accompanying drawing, Fig. 1 and Fig. 2 illustrate'somewhatdiagrammatically and by way of example two constructional forms ofapparatuses for carrying out the method according to the invention.

Referring to Fig. 1, which illustrates the simplest form of apparatusaccording to the invention, I represents a vertical storage tower whichis open at it's top so that the thick pulp to be stored may be chargedinto the tower in a simple manner by the use of any suitable means, suchas a belt conveyer. When it is desired to withdraw a quantity of pulpfrom the tower, a displacement liquid, such as water, is introduced intothe bottom 4 of the tower, as from a tank 8 by means of a pump I througha conduit 5 connected to the bottom of the tower and having a controlvalve 6. The liquid flowing into the bottom 4 of the tower progressivelydisplaces the column of thick pulp 3 upward above the overflow edge 9 atthe top of the tower, so that the pulp flows over said edge onto a beltconveyer III by means of which the pulp is conveyed to the desired placeof use. When the desired quantity of pulp has been emptied from thetower in this manner, the water is drained from the bottom of the towerby opening the valve II in the conduit l2. The water drained from thetower may be used in the plant, preferably as back water, so as torecover the quantity of fiber that remains in the displacement liquid.If the pulp does not contain the quantity of air required for floatingthe pulp on the watenair may be introduced into the bottom of the towerthrough an air conduit 13 having a control valve M. The air ispreferably introduced simultaneously with the introduction ofdisplacement liquid through the conduit 5.

Fig. 2 illustrates a second constructional form of apparatus accordingto the invention, in which means are provided for effecting a fairlyaccurate n l nd mea ring of the quantity of pulp withdrawn from thestorage tower. The same reference numerals as inJFig. 1 are used in Fig.2 to denote similar parts. In the apparatus illustrated in Fig. 2, thedisplacement water is supplied by gravity from a tank [5 through theconduit to the bottom of the storage tower l. The tank i5 is providedwith a suitable water level indicator, such as a glass gauge 56, whichmay be graduated to indicate the volume of water contained in the tank,for instance in cubic meters. Also in this case the introduction intothe bottom 4 of the tower of a certain quantity of water from the tankI5 results in a corresponding quantity of pulp being displaced upwardabove and over the overflow edge 9 at the top of the tower to theconveyer band [0. The accuracy of the measuring of the pulp withdrawnfrom the tower is, of course, dependent upon the upper surface of thecolumn of pulp in the tower being maintained at the same level. For thispurpose there is provided suitable means for fixing the upper level ofthe pulp, such means being illustrated as comprising a rotary scraper I!at the top of the tower, said scraper being driven through suitablegearing 18 by a motor I9. Also .with this constructional form air foreffecting flotation may be introduced through the conduit l3. When thedesired quantity of pulp has been emptied from the tower, the water isdrained from the tower by opening the valve H in the conduit 12, thewater drained 01f being used at any suitable place in the plant. Freshpulp may then be charged into the tower l by means of the conveyer 2.

One of the advantages of the present invention resides in the fact thatthe pulp is always available for distribution from a comparativelyelevated point in the plant, due to the fact that while the pulp isemptied from the tower the pulp is progressively-raised to the topthereof. It is not necessary, therefore, as according to the methodshitherto practised, first to dilute the thick pulp to such consistencythat it may be conveyed by pumping to the place of use, and then againto concentrate the pulp at such place. According to the presentinvention it is possible to convey the thick pulp without changing itsconsistency, for instance by means of a belt conveyer, and to allow thepulp to move by gravity from the conveyer belt to the place where thepulp is to be further treated. As an example, Fig. 2 shows a scraper ordeflector 20 which deflects the pulp from the belt conveyer l0 andcauses the pulp to fall through a chute 2| into a beater 22 in which itis usually desired that the pulp being treated shall have acomparatively high consistency. The advantage above stated becomes, ofcourse, still more marked in such cases when it is desired to use thickpulp alone and where, therefore, the dilution incident to CAD withdrawalof the pulp by means of water jets from the bottom of the receptacle hasresulted in added difficulties which it is desired to avoid.

From the point of View of simplicity and accuracy of measuring thequantity of pulp withdrawn from the storage tower, the present inventionhas a particularly important application to such manufacture where it isnecessary accurately and in a convenient manner to mix several kinds ofpulp stored in different storage towers, for the purpose of balancin theproperties of such pulps. This may be the case, for instance, in acellulose plant where artificial silk pulp is manufactured, and where anequalization of the viscosities is desirable. The same advantage isattained in paper mills where it may be desirable to mix accuratelymeasured quantities of pulps of different qualities.

It will be understood that the constructional forms of apparatus abovedescribed and illustrated in the drawing are only given 'as examples andthat they may be modified in respect of their details within the scopeof the following claims.

I claim:

1. In the cellulose and paper making industry, the method of emptyinghigh consistency fibrous pulp from a substantially vertical storagetower containing a column of pulp charged into said tower from the topthereof, which comprises introducing a liquid under pressure into thebottom of the tower directly below the pulp therein at a rate of flowsuch that a distinct border surface is maintained between the pulp andthe liquid introduced, thereby progressively displacing the column ofpulp upward to the top of the tower so as to eifect discharge of thepulp at the top of the tower.

2. The method of emptying high consistency fibrous pulp from asubstantially vertical storage tower containing a column of pulp chargedinto said tower from the top thereof, which comprises introducing aliquid under pressure into the bottom of the tower directly below thepulp therein, thereby progressively displacing the column of pulp upwardto the top of the tower so as to effect discharge of the pulp at the topof the tower, and introducing air into the bottom of the tower below thepulp therein simultane ously with the introduction of liquid to effect aflotation action between the pulp and the liquid.

3. In the cellulose and paper making industry, the method of emptyinghigh consistency fibrous pulp from a substantially vertical storagetower containing a column of pulp charged into said tower from'the topthereof, which comprises introducing a liquid under pressure into thebottom of the tower directly below the pulp therein at a rate of flowsuch that a distinct border surface is maintained between the pulp andthe liquid introduced, thereby progressively displacing the column ofpulp upward to the top of the tower, and effecting discharge of the pulpby progressively scraping off the upper layer of the column of pulp asthe column rises to the top of the tower.

4. In the cellulose and paper making industry, the method of emptyinghigh consistency fibrous pulp from a substantially vertical storagetower as defined in claim 1, further comprising measuring the volume ofliquid introduced into the bottom of the tower to provide a measure ofthe quantity of pulp discharged at the top of the tower.

5. In the cellulose and paper making industry, the method of storinghigh consistency fibrous pulp in a substantially vertical storage towerand emptying such pulp from said tower, which comprises charging pulpinto the tower from the top thereof to form a column of pulp in thetower, and effecting withdrawal of a predetermined quantity of the pulpstored in said tower by introducing a corresponding quantity of a liquidunder pressure into the bottom of the tower directly below the pulptherein, and by progres sively displacing the column of pulp upward tothe top of the tower by said liquid so as to effect discharge of thepulp at the top of the tower.

6. Apparatus for use in the cellulose and paper making industry storinghigh consistency fibrous pulp, comprising a substantially vertical pulpstorage tower having a uniform cross-sectional area alongits height fromits bottom to its top and having at its top an opening of equalcrosssectional area for charging pulp into and for per-.-

mitting the discharge of pulp from said tower in a lateral direction, alayer of high consistency fibrous pulp extending across the interior ofsaid storage tower to provide a substantially continu ous border surfaceunderlying the pulp to be stored within said tower, and inlet means ofsubstantially lesser cross sectional area connected to the bottom ofsaid tower and communicating directly with the interior thereof forintroducing liquid under'pressure into thebottom of said tower directlybelow said pulp layer therein thereby to progressively displace the pulpin said tower upward to the opening iatthe top thereof.

area along itsheight from its bottom to its top and having at it's topan opening of equal cross sectional area for charging pulp into and forpermitting the discharge ofpulp from said tower, means connected to thebottom of said tower for introducing a liquid under pressure into thebottom of said tower directly below the pulp therein to progressivelydisplace the pulp in said tower upwardly to the opening at the topthereof,

and means connected to the bottom of said tower for effecting acontrolled introduction of air into the bottom of said tower below thepulp therein.

9. Apparatus for storing high consistency fibrous pulp as defined inclaim 6, comprising means for measuring the quantity of liquid intowerdirectly below the pulp therein thereby to progressively displace thepulp in said tower upward to the opening at the top thereof, said meanscomprising a liquid-containing tank, a conduit connecting said tank tothe bottom of said tower, flow-controlling means in said conduit, and aliquid level indicator connected to said tank to indicate the quantityof liquid distroduced through said liquid introducing means 1 into thebottom of said tower.

10. Apparatus for storing high consistency fibrous pulp as defined inclaim 6, comprising means for discharging pulp in a lateral directionfrom said opening at the top of said tower.

11. Apparatus for storing high consistency fibrous pulp as defined inclaim 6, comprising a movable scraper at the top of said tower adaptedto progressively scrape off the top surface layer of the pulp at the topopening of said tower.

12. Apparatus for use in the cellulose and paper making industry forstoring high consistency fibrous pulp, comprising a substantiallyvertical pulp storage towerhaving a uniform crosssectional areaalong itsheight from its bottom to its topand having at its top an opening ofequal cross-sectional area for charging pulp into and charged from saidtank through said conduit into the bottom of said tower.

13. In the cellulose and paper making industry, the method of emptyingmaterial from a substantially vertical pulp storage tower which is openat the top which comprises the steps of providing a layer of highconsistency fibrous pulp which forms a contact surface betweensaidmaterial and a liquid which may be disposed beneath said material insaid tower, and introducing a liquid under pressure into the bottom ofsaid tower directly below the material contained'therein at a rate offiow such that the contact surface provided by said pulp layer will bemaintained, thereby progressively displacing said material upwardly tothe top of said tower so as to permit said material to be dischargedfrom the open top thereof.

14. In the cellulose and paper making industry, the method of emptyinghigh consistency fibrous pulp from a substantially vertical storagetower containing a column of pulp charged into said tower from the topthereof, which comprises introducing a' liquid under pressure into thebottom of the tower directly below the pulptherein,

thereby progressively displacing the column of pulp upward to the top ofthe tower so as to effect discharge of the pulp at the top of the tower,and introducing air into the bottom of the tower below the pulp thereinto effect 'a flotation action between the pulp and the liquid.

J'OHAN CHRISTOFFER FREDRIK CARL RICHTER.

References Cited in the file of this patent UNITED STATES PATENTS

